Polymer compositions and improved process for vulcanization of rubbery hydroxy-contaiing polymers with polyisocyanates



Uite States 3,036,045 POLYMER COMPOSITIONS AND IMPROVED PROCESS FORVULCANIZATION OF RUB- BERY HYDROXY-CONTAINING POLYMERS WITHPOLYISOCYANATES James N. Short, Borger, and Paul W. Solomon, Phillips,

Tex., assignors to Phillips Petroleum Company, a corporation of DelawareNo Drawing. Filed July 5, 1955, Ser. No. 526,116 2 Claims. (Cl.260--77.5)

This invention relates to the production of polymers. In one aspect itrelates to a process for vulcanizing or curing hydroxy-containingpolymers and to the vulcanized polymers produced thereby. In anotheraspect it relates to a novel vulcanizing agent or curative whichdecreases the occurrence of premature vulcanization. In another aspectit relates to a millable and vulcanizable polymeric composition.

By the vulcanization or curing of synthetic polymers and natural rubber,the physical characteristics, such as tensile strength, abrasionresistance, and heat build-up, may be greatly influenced, as is wellknown in the art. Various vulcanizing agents or curatives and otheradditives are mixed with the polymeric compositions prior to the actualstep of vulcanization in order to influence these physicalcharacteristics. The vulcanizing agents chemically react with thepolymeric composition during vulcanization, and the nature of some ofthe reactions is known while the nature of other reactions is uncertain.

In the past, polyisocyanates have been employed in the vulcanization orcuring of hydroxy-containing polymers. However, when these vulcanizingagents or curatives are employed per se the vulcanization or curingoccurs rapidly and at relatively low temperatures. Such procedure oftenresults in premature vulcanization, or scorching, of the compoundedstock prior to the period in the processing cycle when vulcanization isdesired. This scorching prevents (in many instances) the further millingor Working of the polymeric composition.

We have now found that vulcanization of hyd-roxycontaining polymers canbe effected without scorching by employing as a novel vulcanizing agentor curative the reaction product of a polyisocyanate with an activehydrogen-containing compound.

Accordingly, an object of this invention is to provide a process forvulcanizing hydroxy-containing polymeric materials and to provide novelpolymeric materials produced thereby.

Another object is to provide a novel vulcanizing agent comprising thereaction product of a polyisocyanate with an active hydrogen-containingcompound without the tendency for a polymeric composition containingsaid agent to exhibit that premature vulcanization or scorching whichoccurs when polyisocyanates are employed per so as the vulcanizingagent.

A further object is to produce a millable and vulcanizablehydroxy-containing polymeric composition.

A still further object is to produce novel polymeric materials ofdesirable physical characteristics.

Further objects and advantages of our invention will become apparent, toone skilled in the art, from the accompanying discussion and disclosure.

It is known that certain compounds which contain active hydrogen reactwith polyisocyanates to form relatively stable reaction products. Wehave now found that because of the reactivity of these reaction productswith hydroxy groups these reaction products may be advantageouslyemployed in the vulcanization of hydroxy-containing polymers not onlyfor the purpose of yielding polymeric products having desirable physicalcharacteristics but also to prevent premature vulcanization of thepolymeric composition. In the practice of this invention, the reactionproducts to be employed as vulcanizing agents or curatives can beprepared by the well known reaction of an isocyanate with a compoundcontaining active hydrogen. In particular, we have found it advantageousto use at least a stoichiometric amount, and, if desired, an excess, ofthe active hydrogen-containing compounds per mol of the polyisocyanate.The polyisocyanate is caused to react with the activehydrogen-containing com pound at an appropriate temperature. Thetemperature and the time of reaction will be dependent upon the activityof the reactants. The reaction products so obtained are stable at roomtemperature and may be handled without difiiculty.

The polyisocyanates and the active hydrogen-containing compounds can bealiphatic, cycloaliphatic, or aromatic, and they may contain otherreactive groups. While we have found that organic polyisocyanates ingeneral may be used in the practice of this invention, the diisocyanatesare to be preferred because of their availability and ease ofpreparation. Representative polyisocyanates useful in the practice ofthis invention include: mphenylene diisocyanate; p-phenylenediisocyanate; hexamethylene diisocyanate; m-tolylene diisocyanate;p-tolylene diisocyanate; p,p'-diphenylmethane diisocyanate; p,p'-diphenyl diisocyanate; diphenyl-3,3'-dimethyl-4,4diisocyanate;2-chloropropane diisocyanate-1,3;diphenyl-3,3'-dimethoxy-4,4'-diisocyanate; 2,2'-diisocyan-ate diethylether; 3 diethylamine) -pentane-diisocyanate-l,5; 1,5 -naphthylenediisocyanate; pentamethylene diisocyanate; tetramethylene diisocyanate;octamethylene diisocyanate; ethylene diisocyanate;propylene-1,Z-diisocyanate; cyclohexylene-l,2-diisocyanate;xylylene-l,4-diisocyanate; benzenel,2,4-triisocyanate; and the like.

Representative active hydrogen-containing compounds useful in thepractice of this invention include: phenol; 0-, m-, and p-cresol;di-n-butylamine; diphenylamine; piperidine; morpholine;phenyl-beta-naphthylamine; N- methyl-acetamide; N-ethylvaleramide;N-rnethyl-Z-naphthamide; diacetamide; acetanilide; N-phenylbenzamide;succinimide; phthalimide; malonimide; and the like.

The polymeric compositions which can'be vulcanized or cured by thepractice of this invention can be prepared by Well known procedures frommixtures of conjugated dienes and hydroxy-conta-ining monomers or frommixtures of hydroxy-containing monomers and certain othercopolymerizable monomers having an active vinylidene group, e.g., CH CRepresentative hydroxy-containing monomers include:2-phenyl-4-hydroxy-l-butene; 2-(4 chlorophenyl) 4 hydroxy-l-butene;2-(2-brorno- 4-methylphenyl) 4 hydroxy 1 butene; Z-(Z-methoxyphenyl)4-hydroxy-l-butene; 2-(2,4,6-trimethylphenyl)- 4-hydroxy-l-butene; andthe like. Other hydroxy-contaiuing monomers include:dimethylethynylcarbinol; hydroxyethyl arcylates and methacrylates;hydroxyethylstyrene; Z-hydroxyethyl 5 vinylpyridine;N-hydroxyethylaorylamide; N-methylolacrylarnide and the like.

Representative conjugated dienes copolymerizable with thehydroxy-containing monomers generally include those containing from 4 to8 carbon atoms per molecule as exemplified by: 1,3-butadiene; isoprene;2,3dimethyl- 1,3-butadiene; piperylene; 2-methyl-1,3-pentadiene; ch1oroprene; 2-methoxy-l,3-butadiene; 2-ethoxy-1,3-butadiene;2-cyano-l,3-but-adiene; 2-methyl 3 cyano-1,3-butadiene; and the like.

Other representative copolymerizable monomers cont-aining an activevinylidene group include the aryl olefins, esters. of acrylic andsubstituted acrylic acids, nitriles, amides, ketones, ethers, andhalides. Specific examples useful in the practice of this inventioninclude: styrene; nuclear substituted alkyl styrenes;para-chlorostyrene; para-methoxystyrene; methyl acrylate; ethylacrylate; methyl methacrylate; ethyl methacrylate; butyl methacrylate;acrylonitrile; methacryloninile; methacrylamide; methyl isopropenylketone; methyl vinyl ketone; methyl vinyl ether; vinyl acetate; vinylchloride; vinylidene chloride; vinylfurane; vinyloarbozole;vinylacetylene; Z-rnethyl-S-vinylpyridine; and the like.

While we have found that practice of this invention is particularlyapplicable to the processing of a 2-pheny1-. 4- hydroxy-1-butene/1,3-butadiene rubbery copolymer, it is obviously not limited thereto andother polymeric materials herein disclosed are within the scope of thisinvention.

In the preparation of rubbery copolymers of hydroxysuflicient to yield apolymer containing at least 0.009 mol,

and more preferably, at least 0.025 mol of hydroxy group per 100 gramsof rubbery copolymer. It is necessary that at least 0.009 mol of hydroxygroup be present in order that-the desired vulcanization with thereaction products of polyisocyanates with active hydrogen-containingcompounds be obtained. As long as the requisite amounts of thehydroxy-cont-aining monomer and the conjugated diene are present in theinitial charge, as hereinbefore described, the various amounts of theother aforementioned 'copolymerizable materials containing an activevinylidene group can also be present.

The amount of the vulcanizing agent employed in the practice of thisinvention is dependent upon the particular compounding recipe, .theparticular reaction product employed, the extent of, vulcanization orcuring desired, and other considerations which will be evident to thosein the 'art and may be readily determined according to the particularpolymeric product desired. Generally, however, in most instances, theamount of vulcanizing agent is in the range between 0.13 and 5,.mols,preferably in the range between 0.35 and 3 mols, per mol of hydroxygroup in the polymer. The vulcanizing agent useful in the practice ofthis invention may be incorporated into the polymeric composition alongwith other additives such as fillers, sofiteners, plasticizers, etc., byany suitable mixing procedure such as during milling. V

e vuloanizing or curing temperature employed in the practice of thisinvention is generally that which is regarded in the range for rubberprocessing. Ordinarily, this can be in the range between 200 and 400. F.By varyirigthe composition ofthe vulcanizing agent, curing "conditionsmay be varied according to known procedures to obtain the desirablephysical properties in the finished polymeric product. The curing timewill depend upon 'the curing temperature and the particular vulcanizingagent employed. Generally this time will be at least 10 minutes and maybe 48 hours or longer. The curing is continued until the vulcanizate hasthe desired physical properties.

Sulfur is frequently regarded ,as having a deleterious efie'ct on arubber vulcanizate, particularly as regards aging characteristics. Thepresent invention makes avail- :able to'theart a process wherebyfinished polymeric products having good physical properties can beobtained in the absence of sulfur in the compounding recipe. 'Thepolymeric materials obtained by the practice of this invention arenon-corrosive to metals and, therefore, have advantages oversulfur-containing polymers for many applications. It is to beunderstood, however, that the use of sulfur and other additives such asplasticizers, antioxidants, reinforcing agents, vulcanizationaccelerators, etc., can be employed in the compounding recipe. However,these ingredients are not necessary and in some respects it isadvantageous if they are omitted.

Advantages of this invention are illustrated by the following examples.The reactants and their proportions and the other specific ingredientsof the recipes are presented as being typical and should not beconstrued to limit the invention unduly.

EXAMPLE I A 75/25 butadienel2-phenyl-4-hydroxy-l-butene rubber having aMooney value (ML-4) of 56 was obtained by blending severalbutadiene/2-phenyl-4-hydroxy-l-butene copolymers which had been preparedby emulsion polymerization at 41 F. The combined2-phenyl-4-hydroXy-l-butene in the rubber was approximately 10.7 weightpercent (0.072 mols per grams rubber).

Reaction products of hexamethylene diisocyanate and m-t-olylenediisocyanate each with phenol and diphenylamine were used as curativesin the above-described rubber. Synthesis of these reaction products wasaccomplished by heating one mol of the diisocyanate with two mols of thephenol or amine in the presence of a few drops of triethylamine catalystfor 8 hours at C.

(302 F.). Nitrogen analyses are shown in Table I together withtheoretical values:

Table I Nitrogen, weight percent Ourative Diisoeyanate Other compoundnumber Found Theoretical 1 Hexamethylene. Phenol 7.8 7.9 2Diphenylamine... 10.9 11.1 m-Toly Phenol l0. 9 7. 7 4 Diphenylamine-.-10.9

The butadienel2-phenyl-4-hydroxy-1-butene rubber was compounded in blackand gum recipes using the formulations in Table II.

0.69 mol per mol hydroxy group in copolymer.

A blend containing equal parts of Circosol-2XH with Para FluxCircosol-2XH: Petroleum hydrocarbon softener containing hydrocarbons ofhigh molecular weight, in the form of a heavy, viscous, transparent palegreen, odorless liquid of low volatility; sp. gr. 0.940; ayboltUniversal viscosity at 100 F., about 2,000 seconds. Para Flux: Saturatedpolymerized hydrocarbonv The stocks were milled, cured for differentlengths of 90 cure 2 Ten- sile, tion, p.s.i.

Ius, p.s.i.

300% modutaneously when the materials are milled. Snch stocks are,therefore, not processable. Physical properties of the cured rubbers areshown in Tables III and IV.

Elonpercent

sile, tion,

Black Recipe Table IV Gum Recipe (No Black) Tolylenediisocyenate-diphenylamine reaction product Gum Recipe (No black) (1.Stocks in which Table III .Stress-Strain Properties (Original) rmine 0 mn J 8 2 C e 7 1 T p 1 11 e on 050 7. .074 Wou 456 $3 11,1,

1 t 000500 505050 m m n u m016662 821010 mmw (4549389(124333 5 0 5 0 eme )m%w= c7w8)2mwm%9 m H 5275776 8005979 T o. 1 2 1 1 1 2 1 1 1 0 3 0 00.0050 M3 .8620 WOHS. 82111110 5666 3m P 1 1 21 1 1 1 phenol reactionproduct, No. 2. Hexarnethylene diisocyanate-diphenylamine reactionproduct, No. 3.

product, No. 4. m

4 747491236400956 id d d fiA uuomaiamllnmav 3 Poor slab.

Compression set, percent 313601119533718 0&7 &0 0 0 L&4-A 4 A 5 5 1 1111phen0l reaction Mols Mols

256315216424584 e d 5 1 3 0 5 7 O 3 6 506 N w WH776654876W776 m A w w507718280542677 07 6 6 4:L 7 2 9 14 0 .m M%665554%777777 s m m 0 G mu 7321827308535499 9 d 7 13 om&0 2 6 &6 4 3 W 4%33W44533433fl4 F A295112228811581 0 5 2 4-5 4M5 5 6 WW%663333333 O m 148 8130 M996 333452.0 7 1 L L3 27 7 5 0 5 m w 58% 7BH-m mW54fl 767776 e D. A n c Q, MW .w n966 94242814 067376 t e t 15 11959 716406 H "m 57W Mm%65443@777776 S w em 0 r P m S C Q 79 7951 512 52819 9 6 6 d 6 M e MUM n b 6 M%%% nmfififldu aaann e t g U. u I\ w A H F e u T R A k 516350 185585 0 7 45 &7 &Qm:01 0mm a MWMM ZM M D 333333 r. I 11((( O B m m m75 m 7004250 d 6 5 2 &5e WW WH67766 a g n n p A u n m w n 87401703223677. e I a 169528396 m vfimmwu 43277fifi S 8 mm 0 W 51 8152593 3 d 7 & KZLQQQ 8 \1 g 0 0000 A nN u A 132 9155548 1 0 91 58 .W %W- w m 4. e45555 r (1 O CurativeCurative dusocyanates alone are used as curatives instead of thereaction products herein described scorch almost instantirne, andphysical properties dete 1 No. 1. Hexamethylene diisocyanate m-Tolylenediisocyanate 2 Cured at 307 F.

See footnotes at end of table.

catalyst for 8 hours at 150 C. (302 R).

Table lV-Con'tinued Gum Recipe (No black)Cont inued HysteresispropertiesGontinued Shore hardness Scorch at 280 F.

Curative 120' core Cure time Comp. 7 MS 1 4 Minimum Minutes A TFResilience, percent Mooney to scorch 30' 60' 90' 120 No. Mols Orig. AgedOrig. Aged Black Recipeontinued 1 Ouratives as in preceding table. 2 Toosoft. 3 Poor pellet. 4 No pellet.

EXAMPLE II Reaction products of p,p-diphenylmethane diisocyanate withphenol, diphenylamine, and acetanilide, and of hexamethylenediisocyanate and m-tolylene diisocyanate with acetanilide were preparedby heating one mol of the diisocyanate with two mols of the phenol,amine, or acetanilide in the presence of a few drops of triethylamineNitrogen analyses are shown in Table V together with theoretical values:

A /25 butadienel2-pheny1-4-hydroxy-l-butene rubbery copolymer similar tothat described in Examplel was compounded in the following manner usingthe abovedescribed reaction products as. curatives:

Rubbery copolymer ..grams Philblack 0 dn so 'Curative mnls 0.05

The stocks were milled, cured 60 minutes at 307 F, and physicalproperties determined. Milling was easy in all cases. Results are shownin Table VI.

When diisocyanates are used as curatives instead of the reactionproducts described above, they cause almost immediate scorch when milledinto the butadiene/Z-phenyl- 35 4 11ydroXy-1-butene rubber.

EXAMPLE 1H 7 The reaction product of one mol of p-p'-diphenylmethanediisocyanate with two mols of p,-p'-dimethoxydiphenylamine was. used asa curative for a 75/25 butadiene/2- 40 phenyl-4-hydroxy-1-butene rubbersimilar to that described in Example I. The compounding recipe was asfollows:

Rubbery copolymer grams 100 Philblack O ....do-.... 50 45 Curative mols0.05

The stock was milled, cured 60 minutes at 307 F., and physicalproperties determined. Results were as follows:

Reaction products of one mol of m-tolylene diisocya- 60 mate with twomols each of various compounds containing active jhydrogen were preparedand used as ouratives for the 75/25butadiene/2-phenyl-4-hydroxy-1-butene rubber described in Example I. Thecompounding recipe was the same as that given in the preceding example.The stocks Table VI Compres- Tensile, Elon- Perme- Resil- ShoreDiisocyanate Other compound sion set, p.s.i. gation, ATF nent set,ience, hardness -percent percent percent percent -Di hen 1methane Phenol10.5 52.4 0.2 71.3 71 pm p y Dipheynlamine-- 6.5 1, 730 100 36.5 0.175.4 70 1 tanmde 222 5 2 0 a 2%: 23 Hex meth l n rn m-Tily nz 11. 0 2,080 280 115.0 34. 4 55. 7 61 1 Poor slab. 2 Too soft.

Jim. A

were milled, cured 60 minutes at 307 F., and physical propertiesdetermined. No odor or handling problems were encountered during millingor curing of the stocks. Results were as follows:

1 essence of which is that the processing of hydroxy-containingpolymeric materials can be improved by the incorporation into theunvulcanized or uncured polymeric composition, without the tendency forpremature vulcanization to Table VII Comp. 300% Tensile, Elonga- Perma-Resil- Shore Compound reacted with m-tolylene set, modulus p.s.i. tionATF nent set, ience, hardness diisocyanate percent p.s.i. percentpercent percent Di-n-butylamine 6. 3 1, 020 2, 800 510 77. 7 8.0 56. 650 Piperidine 12. 6 780 1, 240 500 169. 6 40. 2 47. 4 63 h/Iornhnl me16. 4 390 580 590 46. 1 58 Phenyl-beta-naphthylamine 6. 7 2, 400 2, 900360 57. 5 0. 8 64. 1 64 Phthalimirle 13. 6 2, 450 120 55.8 0.7 66. 9 761 Pellet split.

The reaction product of m-tolylene diisocyanate with lauryl alcohol wastried as a curative using the procedure described above. Very little, ifany, curing was obtained after 60 minutes at 307 F. as evidenced by acompression set value of 46.7 percent.

EXAMPLE V The reaction product of m-tolylene diisocyanate withphthalimide, described in Example IV, was employed as a curative for the75/25 butadiene/2-phenyl-4-hydroxy-lbutene rubber of Example I using thefollowing conventional compounding recipe containing sulfur:

1 As in Exam le I.

Physical mlxture containing 65 percent of a complex diarylamineketonereaction product and 35 percent of N,N-di pheny1p-phenylenediamine.

3 N cyclohexy1-2-benzothiazylsulfenamlde.

4 0.05 mol per 100 grams rubber.

The rubber was milled, cured at 307 F., and physical propertiesdetermined. Results were as follows:

Cure time, minutes Compression set, percent 19. 7 8. 8 Tensile, p.s.i.,original 1, 400 1, 600 Elon ation, percent, original 110 140 200 F.maximum hot tensile, p s i 850 Tensile, p.s.i., oven aged 24 hrs. at 212F 1900 Elongation, percent. oven aged 24 hrs. at 212 F.-- 110 A TF 58.850. Resilience, percent 65. 9 68. 1 Shore hardnes 72 73. 5

The corresponding run with the same curative in a sul fur-free curingsystem is given in Example IV.

Variations and modifications are possible Within the scope of theforegoing disclosure and discussion, the

occur, a novel vulcanizing agent comprising the reaction product ofp-olyisocyanates with active hydrogen-containing compounds.

Having described our invention we claim:

1. In a method for producing a synthetic copolymer, wherein saidcopolymer is prepared by polymerizing from 50 to 98 parts by weight per100 parts by weight of monomeric material of 1,3-butadiene and2-phenyl-4-hydroxy butene, the latter monomer being employed in anamount sufiicient to yield a copolymer containing at least 0.009 mol ofhydroxy group per 100* grams of copolymer, and said copolymer issubjected to milling and subsequent vulcanization, said copolymer beingreactive with a polyisocyanate, the improvement which comprises addingto said composition during said milling a reaction product of m-tolylenediisocyanate with at least a stoichiometric amount of diphenylarnine permol of said diisocyana-te, said reaction product being employed in anamount in the range of 0.13 to 5 mols per mol of hydroxy group in saidcopolymer.

2. A millab le and vulcanizable rubber mix comprising a copolymerprepared by polymerizing from 50 to 98 parts by weight per 100 parts byweight of monomeric material of a conjugated diene having 4 to 8 carbonatoms per molecule with a hydroxy-containing monomer having a CH =Cgroup, said hydroxy-containing monomer being employed in an amountsufficient to yield a copolymer having at least 0.009 mol of hydroxygroup per 100 grams of copolymer, said copolymer being reactive with apolyisocyanate, and a vulcanizing agent comprising the reaction productof m-tolylene diisocyanate with at least a stoichiometric amount ofdiphenylamine per mol of said diisocyanate, said reaction product beingemployed in an amount in the range of 0.13 to 5 mols per mol of hydroxygroup in the copolymer.

References Cited in the file of this patent UNITED STATES PATENTS2,381,063 Kung Aug. 7, 1945 2,683,727 Masten July 13, 1954 2,683,728Masten July 13, 1954 FOREIGN PATENTS 574,901 Great Britain Jan. 25, 1946150,416 Australia May 3, 1951

1. IN A METHOD FOR PRODUCING S SYNTHETIC COPOLYMER, WHEREIN SAIDCOPOLYMER IS PREPARED BY POLYMERIZING FROM 50 TO 98 PARTS BY WEIGHT PER100 PARTS BY WEIGHT OF MONOMERIC MATERIAL OF 1,3-BUTADIENE AND2-PHENYL-4-HYDROXY BUTENE, THE LATTER MONOMER BEING EMPLOYED IN ANAMOUNT SUFFICIENT TO YIELD A COPOLYMER CONTAINING AT LEAST 0.009 MOL OFHYDROXY GROUP PER 100 GRAMS OF COPOLYMER, AND SAID COPOLYMER ISSUBJECTED TO MILLING AND SUBSEQUENT VULCANIZATION, SAID COPOLYMER BEINGREACTIVE WITH A POLYISOCYANATE, THE IMPROVEMENT WHICH COMPRISES ADDINGTO SAID COMPOSITION DURING SAID MILLING A REACTION PRODUCT OF M-TOLYLENEDIISOCYANATE WITH AT LEAST A STOICHIOMETRIC AMOUNT OF DIPHENYLAMINE PERMOL OF SAID DIISOCYANATE, SAID REACTION PRODUCT BEING EMPLOYED IN ANAMOUNT IN THE RANGE OF 0.13 TO 5 MOLS PER MOL OF HYDROXY GROUP IN SAIDCOPOLYMER.